Hurricane LESLIE (Text)

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HURRICANE LESLIE DISCUSSION NUMBER 27
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012
1100 PM AST WED SEP 05 2012
RECENT TRMM AND SSMI MICROWAVE IMAGES INDICATE THAT LESLIE HAS NOT
FORMED A CLOSED EYEWALL...AND IN FACT...THE INNER CORE CONVECTION
HAS BECOME SOMEWHAT RAGGED. THERE IS STILL SOME INDICATION OF
WESTERLY SHEAR AS WELL...WITH MOST OF THE CONVECTIVE BANDING
LOCATED OVER THE EASTERN SEMICIRCLE. THE INITIAL INTENSITY IS
BEING HELD AT 65 KT BASED ON DVORAK ESTIMATES OF T4.0 FROM TAFB AND
SAB...AND A UW-CIMSS ADT ESTIMATE OF T3.7/4.3.
BASED ON RECENT TRMM MICROWAVE FIXES...THE MOTION IS ESTIMATED TO BE
010/2 KT. LESLIE SHOULD CONTINUE A SLOW NORTHWARD CREEP FOR THE
NEXT 48 HOURS OR SO WHILE IT REMAINS TRAPPED TO THE SOUTH OF A
MID-LEVEL HIGH CENTERED TO THE NORTHEAST OF BERMUDA. THE HURRICANE
SHOULD GAIN SOME NORTHWARD MOMENTUM BY DAY 3 ONCE A DEEP-LAYER
TROUGH DEVELOPS OVER THE EASTERN UNITED STATES. THE GFS MODEL HAS
SHIFTED BACK TO THE EAST ON THIS CYCLE AND IS THE EASTERNMOST AND
SLOWEST OF THE DYNAMICAL GUIDANCE ON DAYS 3 THROUGH 5. SINCE THIS
HAS NOT YET TURNED INTO A CONSISTENT TREND...THE NHC FORECAST IS
BEING KEPT CLOSER TO THE MIDDLE OF THE GUIDANCE ENVELOPE AND IS
VERY SIMILAR TO THE PREVIOUS TRACK FORECAST.
LESLIE IS PRECARIOUSLY CLOSE TO DRY AIR LOCATED OVER THE WESTERN
ATLANTIC. A CROSS SECTION BASED ON GFS MODEL DATA SHOWS AIR WITH
RELATIVE HUMIDITY LESS THAN 30 PERCENT ABUTTING AGAINST THE
CIRCULATION IN THE 250-500 MB LAYER. SINCE MODERATE WESTERLY SHEAR
IS EXPECTED TO AFFECT LESLIE FOR THE NEXT 24 HOURS OR SO...THE DRY
AIR COULD CONTINUE TO SEEP INTO THE CIRCULATION. IN ADDITION...
MICROWAVE DATA INDICATES THAT THE SEA SURFACE BENEATH LESLIE IS
COOLING DUE TO UPWELLING...AND THIS IS UNLIKELY TO CHANGE AS LONG
AS THE HURRICANE MOVES SO SLOWLY. THE NHC INTENSITY FORECAST IS
MOSTLY UNCHANGED FROM THE PREVIOUS ONE AND INDICATES GRADUAL
STRENGTHENING DURING THE NEXT 3 TO 4 DAYS.
LESLIE IS A LARGE TROPICAL CYCLONE THAT IS FORECAST TO GROW IN SIZE
OVER THE NEXT SEVERAL DAYS. THE WIND FIELD OF THE CYCLONE...
COMBINED WITH ITS EXPECTED SLOW MOTION...WILL HELP TO GENERATE
LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND LIFE-
THREATENING RIP CURRENTS ON BERMUDA AND MUCH OF THE U.S. EAST COAST
FOR THE REMAINDER OF THIS WEEK.
FORECAST POSITIONS AND MAX WINDS
INIT 06/0300Z 26.2N 62.5W 65 KT 75 MPH
12H 06/1200Z 26.4N 62.6W 70 KT 80 MPH
24H 07/0000Z 26.8N 62.7W 75 KT 85 MPH
36H 07/1200Z 27.1N 63.0W 80 KT 90 MPH
48H 08/0000Z 27.7N 63.4W 85 KT 100 MPH
72H 09/0000Z 30.5N 64.0W 90 KT 105 MPH
96H 10/0000Z 35.5N 63.0W 90 KT 105 MPH
120H 11/0000Z 44.0N 59.5W 75 KT 85 MPH
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FORECASTER BERG
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